With the ongoing growth in sea-borne trade, utilisation of larger vessels and demand for quick port turnaround, marine terminals are facing significant challenges to cope. Most of the traditional ports still have to rely on old, last generation shipment systems and drafts restriction, thus preventing the industry benefiting from the use of the modern fleet of vessels.
Many existing ports are trying to improve existing approach channels and berthing facilities sufficiently to enable them to handle larger vessels. However, costs for this are not always justifiable economically.
Floating ter minals should be taken into more serious consideration as viable alternatives.
There are many cases in coal, iron ore, copper and agrobulk markets where commodities move solely thanks to the introduction of the floating terminals.
Unlike for other standard vessels’ cranes, the type of facility to be installed on the floating berth would become a key component of the end user’s logistics supply chain.
This brings about a fundamental difference in the designing and selection of cargo handling facilities, which have to be designed specifically for ‘heavy-duty operation, in open sea’. Deep and long lasting marine background is also a vital designing milestone for reliable and smooth operation, consequently.
We know of examples where big mistakes have been made in design and equipment selection. In some cases, the lack of reliability of the envisaged cargo handling facility was not perceived due to an excessive focus on price, or poor assessment of a newly introduced technology which then proved unreliable. While a decrease in accidents and an improvement in the reliability of floating facilities has been experienced in the offshore industry (oil and gas), since the introduction of specific Class, State regulations and the Oil Companies International Marine Forum (OCIMF) guidelines and recommendations, we feel that for dry bulk commodities there is still a ‘home-made approach’, hence room and scope for improvement. Appropriate Class requirements, guidelines and recommendations should be applied, to give and maintain the safety and reliability standards required in the dry-bulk trans-shipment sector as well.
Study and guidelines
To fill in the gap, RINA, the Italian Classification Society (IACS member), and Logmarin are currently developing a comprehensive study aimed at setting up new guidelines for the new generation of ‘open water’ dry bulk terminals to be built.
This initiative benefits from the combined pooling of Logmarin’s shipping logistics marine knowledge and operational background, and Liebherr’s technological skills, together with the experience and know-how of RINA.
For the purpose of the guidelines for the design of a floating berth, data such as:
• The sea state (height and periods for both wind generated waves and swell) the floating units are expected to face (either while in operation or idle due to bad weather) during the life time
• The scope and type of services
• The number of cycles per year etc. is to be taken into account
The buoyant body of the floating facility is free to move on its axis. The rolling, the pitching and the yaw movements are the movements which affect floating crane equipment and mooring appliances at sea the most.
It has been estimated that the floating unit can move over 10,000 times a day, thus causing fatigue to the mechanical components, mooring lines, disruption of operation, breakdowns, and last but not least, discomfort to the crew (especially crane drivers).
The mechanical components of the cargo handling facility, i.e., the crane’s/shiploader’s slewing bearings, gearbox, jib pinions, hoisting winches, etc., are subject to the sea behaviour of the pontoon, accordingly.
Movement dumping devices and suitable dynamic factors which bear such stress and fatigue, should be developed and incorporated in the design of the cargo handling facility, thus maximising the equipment availability for the ultimate benefit of the end user.
Scale of reference-values
There isn’t a standard criterion for whether an operative threshold under which the Off-shore operation can be carried out. This depends on many factors, floating terminal size, dynamic load on crane stability, design, type of waves etc.
Today there are no fixed rules/technical references to certify the quality of floating crane performance in open waters, or a database on which floating cranes should consequently be designed to comply with. We propose to register the superior performance of this new floating crane concept, to use the collected information to construct, for the first time ever, a scale of reference-values for floating crane performance to be sponsored and recognised internationally.
The engineering work incorporates and benefits from the outcome of model tank tests which have been carried out to validate a mathematical sea-keeping model. These have been developed to identify the effect that the various dimensional parameters of both the pontoon and the crane would have on the behaviour of the floating crane while operating in different weather conditions.
The floating crane’s behaviour at sea will be measured by inclinometers and accelerometers, and all the data will be recorded by a data logger. This data will then be used to define the forces and loads the crane is subjected to while at sea, since forces and acceleration are related through Newton’s laws of motion and Einstein’s equivalence principle.
The recorded data, (three axes acceleration and amplitude measurement for the different sea conditions encountered by each specific floating crane) will be then analysed by Logmarin to allow a final tuning and validation of the above mentioned experimental mathematical sea keeping model, enabling the identification of the effects of the variations of the design parameters on the floating crane operational ability for different sea conditions.
The above device will be utilised in order to reasonably improve the design criteria of both the crane and the pontoon, and then sort out the weather thresholds under which the floating crane can safely operate within the new crane limit design criteria in the intended operative location.
The above software could be used to estimate the operational weather working day based on the prevailing weather conditions at a specific site. I could also duly assess the downtime caused by bad weather which might, consequently, affect the project economics.